500693-25-4Relevant academic research and scientific papers
Synthesis and structure of poly(N-propargylbenzamides) bearing chiral ester groups
Tabei, Junichi,Nomura, Ryoji,Masuda, Toshio
, p. 573 - 577 (2007/10/03)
N-Propargylbenzamides having chiral ester groups on the benzene ring, 1-6, were polymerized with (nbd)Rh+[n6-C6H5-(C6 H5)3] to afford soluble polymers with moderate molecular weights (Mn = 34 000-100 000) in good yield. The 1H NMR spectra demonstrated that the polymers have stereoregular structures (cis = 91-100%). The influence of the substitution position for the chiral ester group on the secondary structure was examined. From the comparison of the CD effects of poly(1)-poly(3), the meta-substituted polymer was proven to possess a one-handed helical conformation. When the chiral center was closer to the benzene ring or chiral ester group was bulkier, the polymers showed more intense chiroptical properties. A variable temperature CD spectroscopic study showed that the helical structure of poly(2) and poly(6) was thermally stable. However, the CD spectra of poly(4) and poly(5) were inverted in sign on temperature change in chloroform or toluene, meaning that the helix inversion took place. The temperature of helix inversion could be controlled by copolymerizing with N-propargyl-benzamide (7).
